Since there wasn't a lot of help to get from you guys, I have taken the time to manually compare award availability on ExpertFlyer with what's bookable online through Delta.
For intra-European flights (I didn't check longhaul), business class is coded as booking class O (ExpertFlyer calls this "Business - Classic Awards"), while coach is coded as booking class T (ExpertFlyer calls this "Economy - Classic Europe Award").
If you see O or T class availability for intra-European Air France flights on ExpertFlyer, then those should be bookable through partners.
I'm also not sure if Delta cares about married segments. It seems like there must be availability for each segment separately for it to become available through Delta, but I'm not 100% sure about that (would have been even more work to track all possible combinations).
Thanks for nothing, guys!